Icosahedral quasicrystals for visible wavelengths by optical interference holography

Quasicrystals, realized in metal alloys, are a class of lattices exhibiting symmetries that fall outside the usual classification for periodic crystals. They do not have translational symmetry and yet the lattice points are well ordered. Furthermore, they exhibit higher rotational symmetry than periodic crystals. Because of the higher symmetry (more spherical), they are more optimal than periodic crystals in achieving complete photonic bandgaps in a new class of materials called photonic crystals in which the propagation of light in certain frequency ranges is forbidden. The potential of quasicrystals has been demonstrated in two dimensions for the infrared range and, recently, in three-dimensional icosahedral quasicrystals fabricated using a stereo lithography method for the microwave range. Here, we report the fabrication and optical characterization of icosahedral quasicrystals using a holographic lithography method for the visible range. The icosahedral pattern, generated using a novel 7-beam optical interference holography, is recorded on photoresists and holographic plates. Electron micrographs of the photoresist samples show clearly the symmetry of the icosahedral quasicrytals in the submicron range, while the holographic plate samples exhibit bandgaps in the angular-dependent transmission spectra in the visible range. Calculations of the bandgaps due to reflection planes inside the icosahedral quasicrystal show good agreement with the experimental results.Comment: 12 pages, 4 figure

Ginsenoside Rb1 Preconditioning Enhances eNOS Expression and Attenuates Myocardial Ischemia/Reperfusion Injury in Diabetic Rats

Diabetes mellitus is associated with decreased NO bioavailability in the myocardium. Ginsenoside Rb1 has been shown to confer cardioprotection against ischemia reperfusion injury. The aim of this study was to investigate whether Ginsenoside Rb1 exerts cardioprotective effects during myocardial ischemia-reperfusion in diabetic rats and whether this effect is related to increase the production of NO via enhancing eNOS expression in the myocardium. The myocardial I/R injury were induced by occluding the left anterior descending artery for 30 min followed by 120 min reperfusion. An eNOS inhibitor L-NAME or Rb1 were respectively administered 25 min or 10 min before inducing ischemia. Ginsenoside Rb1 preconditioning reduced myocardial infarct size when compared with I/R group. Ginsenoside Rb1 induced myocardial protection was accompanied with increased eNOS expression and NO concentration and reduced plasma CK and LDH (P < 0.05). Moreover, the myocardial oxidative stress and tissue histological damage was attenuated by Ginsenoside Rb1 (P < 0.05). L-NAME abolished the protective effects of Ginsenoside Rb1. It is concluded that Ginsenoside Rb1 protects against myocardium ischemia/reperfusion injury in diabetic rat by enhancing the expression of eNOS and increasing the content of NO as well as inhibiting oxidative stress

Bioinformatic analysis of the human DHRS4 gene cluster and a proposed mechanism for its transcriptional regulation

<p>Abstract</p> <p>Background</p> <p>The human <it>DHRS4 </it>gene cluster consists of three genes, <it>DHRS4</it>, <it>DHRS4L2 </it>and <it>DHRS4L1</it>. Among them, <it>DHRS4 </it>encodes NADP(H)-dependent retinol dehydrogenase/reductase. In a previous study, we investigated the alternative splicing of <it>DHRS4 </it>and <it>DHRS4L2</it>. <it>DHRS4L1 </it>was added to the gene cluster recently, but little is known about its structure and expression. To reveal the regulatory mechanism of the <it>DHRS4 </it>gene cluster expression, we studied the structure and transcription of <it>DHRS4L1 </it>in the context of the transcriptional behaviors of the human <it>DHRS4 </it>gene cluster. Based on the results of bioinformatics analysis, we propose a possible mechanism for the transcriptional regulation of the human <it>DHRS4 </it>gene cluster.</p> <p>Results</p> <p>The homologous comparison analysis suggests that <it>DHRS4</it>, <it>DHRS4L2 </it>and <it>DHRS4L1 </it>are three homologous genes in human. <it>DHRS4L1 </it>and <it>DHRS4L2 </it>are paralogues of <it>DHRS4</it>, and <it>DHRS4L2 </it>is the most recent member of the <it>DHRS4 </it>gene cluster. In the minus strand of the human <it>DHRS4 </it>gene cluster, a gene transcribed in an antisense direction was found containing a 5' sequence overlapping the region of exon 1 and promoter of <it>DHRS4</it>. By cloning the full length of RNA variants through 5'RACE and 3'RACE, we identified two transcription start sites, within exon <it>a2 </it>and exon 1, of this newly named gene <it>DHRS4L1 </it>using neuroblastoma cell line BE(2)-M17. Analysis of exon composition in the transcripts of <it>DHRS4 </it>gene cluster revealed that exon 1 was absent in all the transcripts initiated from exon <it>a1 </it>of <it>DHRS4L2 </it>and exon <it>a2 </it>of <it>DHRS4L1</it>.</p> <p>Conclusions</p> <p>Alternatively spliced RNA variants are prevalent in the human <it>DHRS4 </it>gene cluster. Based on the analysis of gene transcripts and bioinformatic prediction, we propose here that antisense transcription may be involved in the transcriptional initiation regulation of <it>DHRS4 </it>and in the posttranscriptional splicing of <it>DHRS4L2 </it>and <it>DRHS4L1 </it>for the homologous identity of <it>DHRS4 </it>gene cluster. Beside the alternative transcriptional start sites, the antisense RNA is novel possible factor serving to remove exon 1 from the transcripts initiated from exon <it>a1 </it>and exon <it>a2</it>.</p

EFFECTS OF LOW CONCENTRATIONS OF ROTENONE UPON MITOHORMESIS IN SH-SY5Y CELLS

The mitochondrial toxin rotenone exerts cytotoxicity via overproduction of reactive oxygen species (ROS) and depolarization of the mitochondrial membrane. We investigated the effects of rotenone (12.5, 25, 50, 100 nmol/L) on mitochondrial biogenesis and the potential roles of ROS production in SH-SY5Y cells. Mitochondrial biogenesis was assessed by counting the number of mitochondria, determining protein expression of peroxisome proliferator-activated receptor γ coactivator α (PGC1-α) and its regulator, SIRT1, and oxygen consumption. ROS production and levels of reduced glutathione (GSH) and oxidized glutathione(GSSG) were also determined. Compared with controls, rotenone (12.5 nmol/L) significantly increased the quantity of mitochondria and amount of oxygen consumption, whereas rotenone at \u3e12.5 nmol/L decreased the quantity of mitochondria and amount of oxygen consumption. GSH contents and GSH/GSSG were also significantly enhanced by rotenone at 12.5 nmol/L and decreased by rotenone at \u3e12.5 nmol/L. Except for ROS production and SIRT1 protein expression, all concentration–response relationships showed a typical inverted-U shape. ROS production was continually increased in cells treated with rotenone. These data indicate that low concentrations of rotenone can induce mitohormesis, which may be attributed to ROS production

LC/MS Guided Isolation of Alkaloids from Lotus Leaves by pH-Zone-Refining Counter-Current Chromatography

The traditional methods used in natural product separation primarily target the major components and the minor components may thus be lost during the separation procedure. Consequently, it’s necessary to develop efficient methods for the preparative separation and purification of relatively minor bioactive components. In this paper, a LC/MS method was applied to guide the separation of crude extract of lotus (Nelumbo nucifera Gaertn.) leaves whereby a minor component was identified in the LC/MS analysis. Afterwards, an optimized pH-zone-refining CCC method was performed to isolate this product, identified as N-demethylarmepavine. The separation procedure was carried out with a biphasic solvent system composed of hexane-ethyl acetate-methyl alcohol-water (1:6:1:6, v/v) with triethylamine (10 mM) added to the upper organic phase as a retainer and hydrochloric acid (5 mM) to the aqueous mobile phase eluent. Two structurally similar compounds – nuciferine and roemerine – were also obtained from the crude lotus leaves extract. In total 500 mg of crude extract furnished 7.4 mg of N-demethylarmepavine, 45.3 mg of nuciferine and 26.6 mg of roemerine with purities of 90%, 92% and 96%, respectively. Their structures were further identified by HPLC/ESI-MSn, FTICR/MS and the comparison with reference compounds